In this application, slackless drawbars are most commonly used to connect, in a substantially semi-permanent manner, adjacent ends of a pair of railway cars used in dedicated service. For example, these railway cars may be used in coal or ore operations or in cargo container service. In these particular applications it is not necessary to provide standard Association of American Railroads (AAR) couplers and/or draft gear arrangements since the railway cars are only rarely uncoupled. Nevertheless, it is still desirable to avoid unnecessary impact due to the take-up of slack which can cause rather severe damage to both equipment and/or lading.
The avoidance of shock loads caused by the take-up of such slack between cooperating elements of a railway car coupling system, through which draft and buff loads are applied to a train, has long been a major concern of railway operators. It is recognized in the railroad industry that in some dedicated train operations it is advantageous to avoid the excess weight and cost associated with standard AAR couplers and draft gear arrangements by replacing them with lighter weight, simple drawbars. This means, however, that slack take-up and impact dissipation systems included in the deleted equipment are also eliminated. Therefore, it has been the goal in designing drawbar systems to eliminate as much slack as possible. It is also desirable to keep the apparatus light in weight, strong enough to withstand maximum draft and buff loads and flexible enough to handle side to side and fore and aft angling as required by AAR rules.
It is well known that slackless drawbar systems have been used in the railway industry prior to the present invention. For example, U.S. Pat. No. 4,580,686 illustrates one such system having a wedge-shaped slack take-up member and U.S. Pat. No. 4,996,291 shows a slackless rotary drawbar system. The disclosures of the above patents are incorporated herein by reference and made a part of this disclosure.